CEA targeted Immunotherapeutics is a new project for pur Program Project Grant, however its origins are entirely from the work done previously in the grant. This project is subtitled, Evaluation and Modulation of Immunoregulatory Mechanisms to enhance Immunocytokine Therapy for Colon Cancer, represents a significant translational research effort to carry forward the anti-CEA antibodies into a new arena, Immunotherapy. The project is divided into two major sections, preclinical work to optimize the immune environment under which the anti-CEA-IL2 immunocytokine is administered and finally the conduct of a clinical trial utilizing the knowledge gained in the first section. The first Specific Aim investigates the ability of low dose cytotoxic chemotherapy to enhance the efficacy of immunocytokine therapy with special focus on determining surrogate endpoints suitable for clinical applications. Under this aim two conventional cytotoxic agents will be evaluated, as well as a novel nanoparticle based chemotherapeutic. Using three different types of agents should provide important insights into the mechanism of action of the ability of low dose cytotoxic agents to enhance immunotherapy as well as provide the rational for selecting one of these agents for the subsequent clinical trial. The answers discovered here will also be applied to ongoing clinical immunotherapy studies outside this application, thereby maximizing the benefits from the knowledge gained. Specific Aim 2 investigates the ability of enhancing the efficacy of immunocytokine therapies by specifically targeting regulatory T cells with agents directed at CD25 and STAT-3. This aim is driven by the recognition that IL2 has been shown to induce regulatory T cells, which must at some level compromise the activity of the IL2 based immunofusions. The aim will explore three different types of reagents, anti-CD25 antibodies which have been shown to deplete CD4CD25++ cells in murine models as well as ONTAK, an IL2 based immunotoxin. The investigation of these reagents in this setting should be informative on the modifying the immunoregulatory network for improved ICK activity. As the third part of this specific aim we will investigate the role of STAT-3 in the immunocytokine directed killing, as a way of targeting suppressor T cells with molecular targets. This sub aim will allow us to take full advantage of the pioneering work Dr. Yu has done in this area. The third specific aim will investigate the ability of enhancing the efficacy of immunocytokine therapies by local irradiation, delivered by external beam or radiolabeled antibodies. This aim grew out of increasing evidence that the irradiation of tumors has a variety of immunologic consequences which can be successfully exploited with immunotherapy. This aim will allow us to fully explore the immunological consequences of our radioimmunotherapy and compare them to more conventional external beam irradiation. The last specific aim will conduct a clinical trial with anti-CEA-IL2 immunocytokine based of the previously determined optimal modulation of the immunoregulatory network in patients with metastatic colorectal cancer. This aim is the culmination of the translational research process, investigating our best approaches to treat a significant disease in humans, metastatic colorectal cancer.